1. Field of the Disclosure
The present disclosure relates to instruments for performing minimally invasive surgical procedures. More particularly, the present disclosure relates to an endoscopic electrosurgical instrument for encapsulating and resecting biologic tissue, such as a polyp, that includes a shrinkable pouch for isolating the tissue undergoing resection from the surrounding luminal walls or other adjacent tissue.
2. Background of Related Art
Minimally invasive surgical techniques have been developed wherein the surgical site is accessed by instruments inserted through small incisions in the body, as compared to traditional open surgical procedures where much larger incisions are required to expose the surgical site. Minimally invasive surgical procedures, also known generally as laparoscopic or endoscopic procedures, are often performed in conjunction with electrosurgical techniques. Throughout the present disclosure, the term “minimally invasive” should be understood to encompass both endoscopic and laparoscopic procedures, and the terms “minimally invasive”, “endoscopic”, and “laparoscopic” are to be construed equivalently. Minimally invasive surgical procedures are performed through access devices such as a cannula that is inserted percutaneously into a patient's body. The cannula has a central opening through which surgical objects are introduced and manipulated during the course of the procedure.
Electrosurgical techniques employ radiofrequency (RF) electrical signals in the approximately 200 kHz-3.3 mHz range in connection with surgical instruments, to cut, ablate, or coagulate biologic tissue endogenically. Typically, electrosurgical signals are operated at 100% duty cycle for maximal cutting effect, and are pulse modulated at duty cycles ranging from 50% to 25% for less aggressive cutting, also referred to as blending, or, at a substantially lower duty cycle of approximately 6%, for coagulating. The electrosurgical signal can be applied to the patient via electrodes in either bipolar mode, or monopolar mode. In bipolar mode, both the active and return electrodes are at the surgical site, effectuated by, for example, both jaws of a pair of forceps, such that the electrosurgical signal passes through only the tissue that is held between the jaws of the instrument. In monopolar mode, the active electrode is the surgical instrument at the surgical site, and the return electrode is elsewhere on the patient, such that the electrosurgical signal passes through the patient's body from the surgical site to the return electrode.
Snares are a class of surgical instruments used in the resection of tumors and polyps, particularly those situated on the inner walls of a lumen such as an esophagus, colon, intestine, urethra, blood vessel, or other tubular anatomic structure. Typically, the instrument has at its distal end a wire loop that is positioned around the base or peduncle of the polyp. A pouch or mesh basket for capturing the resected tissue may optionally be attached circumferentially to the wire loop. The proximal end of the instrument is coupled to a source of electrosurgical energy, such as an electrosurgical generator. After the snare is positioned, the surgeon actuates a control on the instrument which causes the wire loop to tighten around the polyp in a drawstring fashion. The surgeon then actuates a second control, typically a handswitch or footswitch, which causes electrosurgical energy to be applied through the wire loop to the operative site, which severs the polyp from the underlying tissue by electrosurgical cutting.
Electrosurgical snares that perform the described technique may have drawbacks. For example, when a particularly large or irregularly shaped polyp is resected, uncontrolled arcing can occur between the polyp and the opposing lumen wall, between the polyp and another anatomical structure located near the polyp, or between the polyp and bodily fluids at the operative site. The uncontrolled dispersion of electrosurgical energy through arcing is undesirable, as it can cause the cutting operation to fail, can cause harmful burns to the opposing lumen wall or other anatomical structures, and can lead to increased operative times and impaired patient outcomes.